I took a project originally done in Nuendo 10.2.10 and opened the same project in both Nuendo 10.3.0 and Cubase 10.5.20 and did mixdowns. Brought the two exports back into Cubase 10.5 and doing a 180 phase on one, they are different but not in any “massive” ways (there’s a sort of noise floor on the meters that stay below -60 with occasional little blips to -50.) Listening to each solo to my ears they do not sound different in any noticeable way. Technically not “bit exact” but nothing anyone would ever be able to hear in a million years.
Near as I can tell I have both systems configured the same; engine is running at 32-bit float, mixdown options were exactly the same (48kHz/16-bit)
Original project is fairly simple; a VO track and stereo music… only using stock effects; Compressor, Maximizer, and some level automation.